Telephone system



y 1929. H.-M. FRIENDLY" TELEPHONE SYSTEM Filed Feb. 28. 1.921 3 Sheets-Sheet l May 21, 1929. H. M. FRIENDLY TELEPHONE SYSTEM Fi led Feb. 28, 1921 Patentfd May 21,1959

UNITED STATES PATIENT OFFICE.

manner at. rmnnmr, or roarmn, oaneon.

summons swarm.

Application filed February 88, 1981, Serial No. 448,712.

while retaining certain operative functions which are known:

Conferences have been held between telephones of private automatic exchanges heretofore by the telephones forming the conference relation gaining connection with a commonly accessible trunk. Heretofore so far as I am awarein order that the various parties to the conference may gain simultaneous connection with. the common trunk, the trunk is not made busy incident to it being seized by the first party gaining connection with it, or by any of the parties gaining connection with it subsequently successively. The ractice has been, whereconference trunks ave been provided in private automatic exchange equipments, to have the conference trunk at all times accessible to all the connectors in two-figure capacity private branch'exchanges, and accessible to all the first selectors in three-figure capacity private branch exchanges.

It is manifest from the foregoing that it will be impossible under thev above method of conference operation to hold conferences that cannot be intruded upon by unauthorized permns through the telephones of .the private branch exchange because they can unrestrictedly gain access to and connection with the conference trunk either before a conference has been called or after it is under way.

The present invention is particularly directed to provide means whereby'the party calling the conference can, as heretofore practiced, request the parties desired in conference to each call the same predetermined number through the agency of the calling device at their telephones and thereby gain telephonic connection with the conference trunk. Now under the new arrangement contemplated in the present invention the arty calling the conference (who will be iereinafter referred to as the supervisor or the su ervising party) will at any time, e ther fore or after the other parties, (or single party only) have complied and are in common telephonic connection with a first branch of .the conference trunkand with each other,"call a second predetermined telephone number reserved exclusivelyto the supervising party, and thereby gain telephonic connection with a second branch'of the conference trunk tele honically related to the other (first brancli to which tie other parties connect. After the supervising party ascertains that all the requested parties are on the first branch of the conference trunk and in telephonic connection with him, and, of course, knowin how many such arties there are, he will die 1 for exam e and thereby initiate the functioning o a first hunting or settingof the conference trunk switch, which switch will in turn set up a I condition in a second switch indicative of the actual number of parties connected with the said first branch and automatically return to normal indexing t e number of parties ordered on the first branch of the conference trunk, whereupon the said first switch will be caused to step a corresponding number of steps, completing a circuit through the said second switch and to a tone-controllin relay which will apply a tone to the second branch of the conference trunk, audible to the-supervising party: The said tone will be thus applied providing no more or no less arties are-connected with the first branch 0 the conference trunk than indexed by the di it dialed. If, upon attempting to verify t e number of parties (or the single party thereon) on the rst branch of the conference trunk as set forth, the tone does not become audible,'the supervising party will then know that'some ot er party, unauthorized, is connected with the conference trunk, or that all supposed to be are not. Steps can then be taken to investigate. As Wlll appear presently the tone is applied to the second branch audible to the supervising part secretly, not audible to the parties connecte with the first branch, so the supervising party can have any investigations made while the condition found remains unknown to others.

In case the supervising party obtains the tone, indicative that the pro er number of parties are in conference re ation, dialing osition. He will then dial a digit the supervising party digit 1 will cause the tone to cease and the conference can proceed secretly, and furthermore, the conference 'trunlr will be barred from seizure thereafter, however, roviding for any of the parties on the first Eranch of the conference trunk disconnecting therefrom without unguarding the conference trunk against. its seizure subsequently, or in lieu of the disconnecting art p T e present invention also contemplates a feature, effective at will through the manipulation of switch elements. Under the alternative o erative method, consequent upon first calling digit 1 as before set forth, a specific tone source in-- dicative of the number of part1es connected with the common branch ofthe conference trunk will be secretlyievidenced to the saide can then call-digit su ervising party. B so the conference and the tone will cease,

can proceed.

Lamps are provided, located singly or m multiplicit visible to a certain partyor parties, w 'ich will index the number of arties on the common branch of the conerence trunk, depending upon which lamp or lamp set is glowing.

A step-by-step counting device is provlded to integrate the number of busy test contacts encountered, the latter busy test contacts being indicative of the number of telephones connected to the first or common branch of the conference trunk.

Referring 'to the accompanying drawings:

Fig. 1 shows a calling telep one leading to a pro-selector or so-called line-switch in access to a pluralit of connectors, one connector only of whic is shown;

Fig. 2 in conjunction with the right-hand portion of Fig. 1 shows a schematic representation of five connectors accessible to a conference trunk and other associated, cooperating equipments necessary in carrying out the present invention. It will be noted that Fig. 2 attaches to the right of Fig. 1 so that the lines extending toward the margins of the sheets register.

Fi 3 which attaches to the right of Fig. 2 so t at the lines extending towards the mar- 'ns register, shows the busy contact countmg device and register with means for applying tone sources as contemplated in the present invention.

Fig. 4 is a schematic detail plan view of one of the levels of contacts and its cooperating wiper shown in the automatic rotary switch elements F and G represented in Fig. 3. The elements F and G also have the function of step-by-step calling-device control..

. To simplify the drawings and descriptions,

the battery (which has its negative pole ground are shown as indegrounded), and pendent sources throughout, wherever applied, but it is to be un erstood that the sys- 1',714,soa.

ing the opposite terminal of which is shown applied to grounded battery or to ground, the described circuit is to be considered as traced to ground through the winding and battery, or direct to ground, as indicated.

Where a circuit is traced through an armature of a relay to an engaged contact, the contact'only will generally be designated. That is, if the armature is attracted the make contact only will be referred to generally and if the armature is normal the resting contact only will be designated generall eferring agan to the various gures:

In Fig. 1 the calling telephone T (of which there are a plurality 1n the system) is of the usual series type, having a calling device (sometimes termed a dial or sending device) of the general class, as shown in British patent to Dicker, No. 29,654 of 1910. The preselector (also called a line-switch) PS is of the general class, as set forth in U. S. Letters Patent to Lamb No. 1,193,160, granted August 1, 1916. The connector A is of the eneral class as set forth in U. S. Letters atent to Deakin No. 1,164,479, granted December 14,1915.

The said connector A has access to a plurality of bank contact sets on a plurality of levels. Usually ten levels would be provided, each having ten sets of bank contacts. The contacts shown are to be assumed as the last three sets of contacts of the first level. The connector A will function as a selector on certain levels, depending upon the adjustments of its off-normal sprin sets 2 and 3. For example, if s rings 2 an 3 are adjusted to close upon the s aft of the connector attaining the tenth level, upon which perhaps are outgoing trunk lines, the switch will, upon its shaft attaining the tenth level, forthwith start automatic rotation, seeking an idle trunk to seize. We are, however, not particularly concerned with the operation of the connector A functioning as a trunk-huntingselector, inasmuch as. this function is not a function directl related to the present invention. However, t e off-normal springs 2 and 3 are, in addition to the stated possible adjustment affecting the tenth level, arranged to close upon attaining the tenth rotary (position when functionin on the first level. f course, a supplementa set of springs in multiple relation, to the sets 2 and 3 may be. provided to operate independently of 2 and 3 by cam action from the shaft, fvlleil the switch is functioning on'thc first eve I Referring now to Fig. 2, B, C, D, and E each indicates a connector as shown in A of Fig. 1, and in addition, all the other cooperating elements shown in 7 manifest that Figs. 1 and 2 represent aprivate automatic exchange system having a plurahty of telephones of the stated type,

III

Fig. 1. It will thus bev iso each connected with its individual pro-selector and each said pre-selector has access to each of five connectors represented by A, B G, D and E. Further, that each of the said connectors has access to corresponding bank contacts commonly related to the two branches of the conference trunk. 7

It will be observed presently that as man parties as the connector capacity will permit may gain connection with the first branch of the conference trunk used generallyby the partiesof the conference, but that only one party at a time can gain connection with the other (second) branch reserved to the supervising party at. a random one of said telephones.

Referring to Fig. 8 switch Fv is'a step-byste switch having five wipers rigidly attac ed to its shaft, each wiper cooperating with a level of six bank contacts spaced equally and directed radially from the eircumfer-- ence of an insulated holding element. A drive-magnet M upon being energized (or deenergized after energization) causes the five wipers to advance one step into engagement with a successive set of five cooperating bank contacts, so that if six impulses are im arted to the shaft revolvably carrying the ve attached wipers, through the agency of the magnet M, the said wipers will have successivel en aged each of its respective cooperating an contacts and have arrived back u on their normal resting bank contacts. This function will be thoroughly understood by referring to Fig. 4 and it may also be considered in more detailby referring to the cited patent to Lamb, the relationship between the magnet M- and-the shaft carrying the wipers being the same in switch F of the present invention as set forth in the said cited patent. Excepting, however, that in the present invention it is preferred (though not necessary) to have the wipers driven forward consequent upon the de-energization of the motor magnet M and the motor magnet M, rather than upon their energization.

Off normal spring group designated 0N3 operates consequent to any off-normal movement of the wipers of switch F.

Switch G is a-similar switch to switch F in its general mechanical functioning, however, having but two wipers and cooperating levels of bank contacts. 1

It is thought that in view of the foregoing general descriptions the operation of assumed supervisor will instruct (by calling over the.

telephone or otherwise) the three parties to come on the conference trunk, which they will each do by calling telephone number 19. For example, when party at telephone T removes the receiver from the switch-hook,

ing of relay N, conductor 5, sprin .6,'conductor 7 ,wiper 8, conductor 9, throng telephone I T, conductor 10, wiper 11, conductor 12, contact 13, conductor 14 to the lower-winding of relay N, causing it to actuate. A circuit can thereafter be traced from the winding ofslow-releasing relay B, armature 15, conductor 16, togrounded armature 17, causing said relay B to actuate. This will apply ground from contact 18 to conductor 19, wiper 20 to the winding of the cut-on relay of the preselector PS, to disassociate'the line-relay of the pre-selector, in a manner" well known. Upon the party at telephone T manipulating the calling device thereat to effectuate one $en impulse constituting digit 1, relay will deactuate and reactuate one time, applying ground from armature 17 conductor 16, armature 15, contact 21, side-switch wiper 22, winding of relay 0, winding of the ver- .tical magnet V, side-switch wiper-23, to

grounded batter causin the vertical magnet to step the sliaft of t e connector carrying wipers 24, 25 and 26 one vertical ste and into registry with the first level of ban contacts. At the time the vertical magnet is energized slow-releasin relay C actuates and applies ground from its armature 27 tov the winding of the private magnet P, causing it to attract its armature preparatory to ermitting the side-switch wipers 22, 23 an 28 to move into their second positions respectively, consequentto its deenergization and the retraction of its armature resultant thereto. The latter occurs the period of relay C following its de-energizationupon the reestablishment of the energizing circuit for relay N upon the calling device at telephone T returning to normal. Upon the party at the calling telephone T transmitting digit-9 in the manner as before, this time etfectuating nine open impulses wherein relay N will dea'ctuate and reactuate nine times consequent thereto, a circuit will be established upon each retraction of relay N from grounded armature 17, conductor 16, armature 15, contact 21, wiper 22 (in second position) winding of relay G, armature 29, windingof rotary magnet It, side-switch wiper 23to grounded battery, causing the rotary magnet to step the shaft in nine rotary steps, wipers 24, 25 and 26 engagin bank contacts .30, 31 and 32 respectively. ank contact 30 has battery potential onit, received through resistance 201 over conductor 202. Uponthe retraction of relay C, its period after its last energization impulse private magnet P will, deactuate as -before and permit the side-switch wipers 22, 23 and 28 to advance into their third positions respectively. A circuit can now be traced'from bank contact 30 (upon which is battery potential), wiper 24, 51(16- switch twiper 28, inside winding of relay H, contact 33 of private ma net, armature 34, conductor 19 to grounded contact 18, causing relay H to actuate and look its outside winding .to armature 35 and to grounded conductor 19. Contact 36 will become rounded upon armature 35 applying groun to sideswitch wiper 28, wi er 24, bank contact 30, conductor 202 to ban z contact 203. A circuit can now be traced from signalling current generator G, armature 37, conductor 38, armature 39, conductor 40, contact 41, wlper 26, bank contact 32, conductor 42, retardation coil 205, armature204, conductor 206,

6 bank contact 31, wiper 25, conductor 43, ar-

mature 44, conductor 45, armature 46 conductor 47, contact 48, contact 49, to the inside winding of relay F, causing relay F to actuate. Relay F is so designed as to not actuate thus included in a signal circuit including a condenser, as for example when ringing upon conductors including a telephone similar to T. A telephonic circuit can now be traced from telephone T to spring 6, as described, condenser 50, conductor 51, armature 52, conductor 53, contact 48, conductor 47, armature 46, winding of shunted relay G", wiper 25, bank contact 31 to conductor 206 and from conductor 42, bank contact 32, wiper 26, contact 41, conductor 40, armature 39, conductor 38, armature 37, conductor 55, condenser 56, contact 13 to the telephone T over the circuit described.

It will next be assumed that connectors B and C (bearing in mind that they are similar to connector A and that they are accessible to telephone similar to T and line switches similar to PS respectively), are manipulated as described in relation to connector A and that, therefore, wipers 207, 208, and 209 are in engagement with bank contacts 210, 211, and 212 respectively and that the conductors 42. and 206 are in telephonic relation with the telephone leading to connector B. Also.

wipers 213, 214 and 215 are in engagement with and that the conductors 42 and 206 are in telephonic relation with the telephone leading to connector 0. Therefore, telephone '1 and the two similar telephones leading through connectors B and C respectively are in telephonic relation through thecommon trunk conductors 42 and 206 and that parties thcrcat may converse mutually audible.

It will be assumed that connector A is in normal position and that the party gaining telephonic connection from telephone T through it to the trunk conductors 42 and 206 had gained connection through the telephone and pre-selector leading to connector D and that wipers 219, 220, and 221 were in engagement with bank contacts 222, 223 and 224 respectively and that, therefore, the telephones connected through connectors B, G

bank contacts 216, 217, 218 respectively.

and D respectively are in telephonic relation mutuall audible.

' It will now be assumed that the party calling or supervising the conference is at telehone T and that he manipulates the calling evice thereat to effectuate tele hone num-. ber 10?. The connector A will unction in a manner as before described when the calling device was manipulated to effectuate telephone number 19. However, the wipers will have been moved to the tenth rotary position alon thefirst level in lieu of to the ninth position thereon. It will be borne in mind that off-normal spring sets 2 and 3 are designed to close their contactsupon the wipers rotating to the tenth rotary position on the first level, and therefore, these contacts will now be closed. Wipers 24, 25 and 26 are in engagement with bank contact 60, 61 and 62 respectively. Relay J will actuate due to the closure of oil-normal spring set 2. An inert circuit path can now be traced from battery through resistance 225, conductor 226, bank contact 60, wiper 24, side-switch wiper 28 in second position, armature 63, spring 64,- to the Winding of the private magnet, the private magnet not energizing, and therefore retracting consequent to the retraction of armature 27, as before described.

This will permit the side-switch wipers 22, 23 and 28 to advance into their third positions respectively and cause relay H to actuate as before described; A circuit can now be traced from grounded contact 18, conductor 19,-armature 35, contact 65, armature 66 through off-normal springset3 to the winding of relay K causing it to actuate. A circuit can now be traced from the lower winding of relay 230, conductor 231, bank contact 61, wiper 25, winding of shunted relay G", armature 46, conductor 47, spring 6, conductor 7, through the telephone T, conductor 12, armature 39, conductor 40, contact 41, wiper 26, bank contact 62, conductor 68 to the upper winding of relay 230, causing said relay 230, and also relay G" in the connector A to actuate. A circuit can now be traced from the winding of relay B to grounded armature 69. The latter will ensue before the period of relay B which dcenergized dependent upon relay N which was disassociated from its described energizing circuit consequent to the actuation of relay K. Ground will thus be maintained from grounded contact 18 to conductor 19 and to the outside looking winding of relay H, dependent upon relay G. At the time relay 230 actuates it applies its grounded armature 232 to the contact leading to the winding of the slowreleasing relay 233, causing it to actuate.

It is thus manifest that a telephonic circuit now exists from telephone T to conductors 231 and 68 and that relay 230 is energized in series with the telephone T and is therefore in control of the calling device 'at tele hone T. It will be further noted that con uctors 42 and 206 are related tele honically to conductors 68 and 231 throu condensers 234 and 235 res ectively, an therefore, the telephone '1 an the telephones (not shown) assumed connected to the trunk condeactuate and reactuate one time, applyingground from its armature 232 to armature 236, winding of slow-releasing relay 237, conductor 238, to the winding of motor magnet M, causing it to actuate and advance wipers 239 to 243 inclusive one rotary step, into engagement with bank contacts 203, 244 to 247, inclusive respectively.

It was described how bank contact 203 became grounded consequent to connector A seizing after its wiper 24 en aged bank con- -tact and it may be state here that bank contacts 248, 249 and 250 become rounded similarly consequent to connectors G and D seizing as set forth herein. It is to be remembered here that bank contact 203, under the assumed condition now existing doesnotconstitute ground potential, because wiper 24 is assumed to be in engagement with bank contact in lieu of bank contact 30 first assumed so that bank contacts 248, 249 and 250 are the only bank contacts constituting ground potential engageable to wiper 239.

Upon the motor magnet M causinglthe wipers 239 to 243 inclusive, to advance into engagement with contacts 203, 244 to 247 inclusive, res )ectively, the following condition will ensue, wearing in mind that bank contact 203 has battery potential, derived through resistance 201; ground from armature 251, conductor 252, wiper 240, bank contact 244, conductor 253 to the winding-of relay 254 will energize the latter relay and cause it to actuate. A locking circuit for relay 254 1s closed from its winding, contact 262 to grounded conductor 252. In View of the slowreleasing characteristic of relay 233, it Wlll remain sustained, after it becomes actuated, over all lapses of ground from armature 232 such as will occur upon relay 230 respondlng to manipulations of the calling device at telephone T and therefore, the ground applied from armature 251 to conductor 252 will; endure until the circuit including the windings x of relay 230 is open for a prolonged period,

as for example, )y the supervising party at p telephone T restoring the receiver on the switch-hook. Contacts 60, 263 to 266 1nto the actuation of the'motor magnet elusive, attached to common conductor 226 will, of course, constitute ground potential, thus guarding the supervisors branch of the conference trunk against intrusion by reason I ofconnector A maintaining ground potential" on wiper 24 (and en aged bank contact 60) inthe mannerset fort hereinbefore. Groundfrom armature 267, conductor 268, bank contact 246, wiper 242, armature 269 to the winding of motor magnet M will'cause the said motor ma et to automatically actuate and advance t 1e wipers 239 to 243 inclusive a rotary step into engagement with-bank contacts 248, 270 to 273 inclusive respectively. Conse uent its armature 269 will. attract from its resting contact and open its described energizin circuit, causing it to deactuate and reesta lish its energizing circuit, whereupon it will again actuate, advancing the said wipers 239 to 243 inclusive, an additional rotary step into engagcment with bank contacts 249, 274 t6 277 inclusive respectively, whereupon the same functionin of the motor magnet M as described wi 1- again ensue, advancing the said wipers one rotary step; this functioning continuing until the said wipers have left bank contacts 278 to 282 inclusive respectively and have engaged the respective bank contacts upon which they normally rest, as shown in the drawing.

Due to relay 254 being locked as described, a circuit path now exists from wiper 241, contact 262 to grounded conductor 252; this circuit becomin established upon relay 254 ac- 100.

tuating inci cut to the wiper 240 engaging bank contact 244, so that normally w'i er 241 constitutes batteirly potential derived t rough the relay 254. owever, upon wiper 241 returning to and engaging the bank contact upon which it normally rests, it will apply its ground potential over conductor 283 to the winding of relay 284, causing it to actuate and lock through its contact 285 to grounded conductor 252. A circuit can now be traced from the winding of relay 286 to grounded arma- I ture 267, causing it .to actuate, and apply ground from conductor 287- to conductors 288 to 292 inclusive, applying this ground potential to bank contacts 203, 248, 249, 250 and 27 8, also to connector bank contacts 30, 210, 216, 222 and 293 in lieu of battery potential normally existing on the said contacts. It will thus be seen that the bank contacts of the conference trunk, (conductors 42 and 206) are now guarded against seizure by any connector normally accessible thereto in plurality, and that therefore, only those attaining connection with the conference trunk revious to'the su ervising party dialing digit-1, from tclep one T, can gain connection with it; this until the said supervising arty at telehone T restores the receiver t ereat on the switch-hook and causes relay 233 to deactuate and unlock relay 286.

It has been set forth that bank contacts- ,248 to 250 inclusive, constituted ground po- ,tential before relay 286 actuated, resultant to the actuation of relay 284; this due to bank contacts 210, 216'and 222 having been seized by connectors B, O, and D. With this latter in mind it will be clear that when the motor magnet M drove the wipers 239 to 243 inelusive, wiper 2339 derived groundpotentialsuccessively from contacts 248. 249 and ;,250.

. and communicated this groundseries over conductor 294, contact 295 to the-winding I of motor magnetMQ-causing itto actuate and deactuate three times, stepping its wipers 232, magnet M the relay 284 actuates.

296 and 297 into engagement with bank contacts 298 and 299 respectively.

It may be mentioned'liere that the object of includin conductor 294 throughrelay contact 295 19 to insure that .no impulses-can be imparted to the windin gtherwise, when magnet M iscaused to step controllably, responsive to each impulse a plied from armature woul actuate. upon wiper 239 agam encountering the grounded bank contacts engaged in its travel in the cycle there are grounded bank contacts engaged by wiper 239 in its cycle. That is to say, the

completed automatically after its initial impulse, as set forth. I

By reference to Fig. 4 it will be manifest that the contacts are successively engaged and. that the wiper does not enga e ad acent contacts co-incidently. It may e further stated here that the described movement-of the sets of wipers driven by the motor magnets M and M respectively, are driven rotarily consequent upon the armatures of the de-en-,

said motor magnets retractin upon ergization, though it is entire y practicable to have the wipers driven consequent upon the energization directly; Thus, it will be manifest from the foregoing that upon the supervising party dialing di it 1 the switch F will, responsive thereto, a vance one. rotary step and then automatically advance by steps until it reaches its normal position. At the same time, switch G will cause its wipers to be advanced as many rotary steps as wipers of switch G will be advanced as many rotary positions as there are connectors in engagement with the conference trunk, not counting the connector A on the second branch controlled from telephone T by the supervising party. here bem three parties to the conference, exclusive of t e supervising party, the supervising party will now mam pulate the calling device at his telephone T to effectuate three open impulses constituting digit 3 which latter digit indexes the number of parties in the conference excluding the supervisin party. At each open impu se, relay 230 will eactuate and then reactuate uponthe closure, applying ground from its armature 232,

of magnet M after armature 236, winding of relay 237, conductor 238 to the winding of motor magnet M,

causing the said motor ma net to be energized and de-energized three times, thereby steppmg the wipers 239 to 243 inclusive, three rotary steps into engagement with bank contacts 249, 274 to 277 inclusive respectively. I

It will be'noted here that conductor 268 does not now constitute ground potential and that, therefore, the automatic interru ter circuit for motor magnet M described be ore as leading to 'armature 269 is now open at armature 267; After the period of relay 237 a circuit can be traced from grounded armature 300, wiper 296, bank contact 298, conductor 301',

bank contact 277 'wiper'243, conductor 302,

contact 303 to the winding of relay 304, causing it to actuate. A circuit can now be traced from tone source T2, conductor 305, switch arm 306, spring 307, conductor 308, armature 309, conductor 68 over the described path including the telephone T to the lower winding of relay 230, audible to the supervising party. It will be noted'here that due to armatures 309 and 310 being attracted the links between the branches'of the conferonce trunk including condensers 234 and 235 willbe 0 en, and therefore, the tone will not be audib e to the arties called into the com ference (and any mtrudin party) connected with the firstbranch, comfuctors 42 and 206.

The tone received by the supervising party will indicate or verify that there are but three parties on, tl 1e conference trunk exclusive of the supervislng party. It is clear that if the supervising party had ordered four parties in on the conference, but only the three exampled com lied, and that the supervising arty, thereore, in verifying, dialed digit 4 in lieu of digit 3, as before, wiper 243 would be caused to rest on bank contact 312 in lieu of bank contact 277, and therefore, in view of the position of wipers 296 and 297 on bank contacts 298 and 299 re spectively, the described circuit from grounded armature 300 to the windin' of relay 304 would not be completed, and t at therefore,

due to the tone not being received the supervising party-would know that the parties 1 were not all present, or as shall be clear pres- 1' ently, that some unauthorized party had gamed connection with the conference trunk.

erence trunk throughconnector E and that,

therefore, wiper 313 caused bank contacts 293 and 278 to constitute round potential; this before the actuation o relay 286. Then, wiper 239 will encounter four grounded bank contacts in lieu of three, as before described and that therefore, four ground impulses will be applied to the windin of motor magnet M causing it to advance its wipers 296 and 297 into en agement with bank contacts 314 and 315 in ieu of bank contacts 298 and 299 respectively. Now, u on the su ervising party dialing di it 3 (or digit 1 three times successively the circuit from armature 300 will not be complete because wiper 243 will rest on bank contact 277. If now, the supervising party dials digit 1, causing wiper 243 to advance and engage bank contact 312, the circuit from grounded armature 300 will complete its circuit from wiper 296, bank contact 314, conductor 316, bankcontact 312, wiper 243, conductor .302, contact 303 to the windin of relay 304. The relay 304 will actuate an apply the tone T2 audible to the su ervising part as set forth before. This wi verify that t ere are four arties on the conference trunk, whereas he had ordered but three to come thereon, and that, of course, steps may be'taken to locate the intruder.

From the foregoing it is manifest that if only the three authorized parties are on the conference trunk the tone will index the fact. This tone will continue audible until the supervisin party dials digit 1 to cause motor magnet hi to advance its wipers one rotary step, thereby opening the traced path including the winding of relay 304 and causing it to deactuate and reestablish the conference relation and disconnect the tone source T2 so that the conference may proceed. It will be' obvious that in practice the supervising party may after dialling digit 1 to initiate the functioning of switch F, follow by dialling digits 1 successively until a tone s obtained. Then, the number of times dig1t 1 is dialed to attain the tone condition after initiating the movement as stated, w1ll index the number of parties on the first branch of the conference trunk.

It will be manifest, presently, that the supervising party can, in lieu of dialling digit 1 to disassociate the verifying tone, replace the receiver upon the switch-hook and then initiate a new ealland come in on the second branch of the conference trunk as before, by

dialing 10. In this connection it may be mentioned that had the supervising party not ounded and break its energizing circuit and advance the wipers 239 to 243 inclusive an additional rotary step, whereupon the same functionin will take place as hereinbefore describer causing .the shaft to com lete a cycle and return to its normal position as shown in/the,

drawing.

Relay 237 is not essential to the carr ing present invention. It is introduced to insure that the path traced including the winding of relay 304 shall not become closed until a brief period after wi er 243 of switch F engages a cooperating ank contact. This period is approximately the period'of relay 233. Relay 237 will thus sustain over the current lapses of a digit series, so thereean be no brief period of confusing tone applied-by the action of relay 304 audible to t e supervising party, should a circuit condition including the winding of relay 304 be possible before the wipers of switch F have come to final rest consequent upon the supervising out of'the salient operative features 0 the party sending the second digit indexing the num er of parties instructed to come on the conference trunk. This condition could occur if but three of the four instructed parties came on the conference trunk. That is, as the wiper 243 engages and passes contact 277 in reaching bank contact 312 while wiper 296 is resting on bank contact 298, the path ineluding the winding of relay 304 will be momentarily completed from grounded armature 300, wiper 296, bank contact 298. conductor 301, bank contact 277, wiper 243,'conductor 302, causing relay 304 to actuate and apply the tone as before set forth, audible to the supervising party. It will be noted that when the tone is applied audible to the supervising party that the link between conductors 68 and 42 including condenser 234 and the link between conductors 206 and 231 including condenser 235 willbe opened at armaturcs 309 and 310 respectively. Thus. while the supervising party is verifying, those on I the conference trunk will not hear the tone.

Retardation coil 205 is removed from the bridge incident to the actuation of relay 284, and therefore does not derive current during the period of the conference. It may thus be of low ohmic obstruction to insure the ring-cut-ofi' relays (as F) operating while current from retardation coils (as U) of other seized connectors is being derived through it.

We will now assume that after the conference has been completed with the three anthorized parties that the supervising party I bank contact 299, this circuit is contained through armature 317 to the winding of motor magnet M', causing it to energize and attract its said armature 317 and open the said energizing circuit, whereupon wiper 297 will advance into engagement with bank contact 315, causing the said described energizing circuit of motor magnet M to again be established and interrupted, driving wiper 297 into engagement with bank 'contact'321, thus again establishing the energizing circuit of motor magnet M whereupon it will actuate and interrupt and drive'wiper 297 into engagement wlth bank contact 324, upon which it nlormally rests, having thus completed its eye e.

Due to ground having been removed from conductor 252, by'the retraction of armature 251, the locking ground of rela s 286, 254 and 284 is removed and the said re a s retract. However, we are concerned chie y at this juncture with the retraction of relay 284 which will establish a circuit from grounded armature 267, conductor 268 to bank contacts 281, 319, 276, 272 and 246. Remembering that wiper 242 now rests on bank contact 319 (it having been stepped from bank contact 276 to cease the tone), the circuit may be traced to wiper 242, armature 269 to the motor- 1 magnet M, causing it to ener izeand attract its armature 269 and inci ently interrupt the said circuit, whereupon it will retract and advance wiper 242 into engagement with bank contact 281, re-establishing the energizing circuit to the said motor magnet M, causing it to function as last before described, this time advancing Wiper 243 into engagement with bank contact 325, which is its normal resting position; It will thus be noted that upon the retraction of relay. 233, motor magnets M and M will start automatically functioning and so continue until they have caused their respective cooperating sets of wipers to have attained their normal positions.

It will be clear that during the progress of the conference, after the supervising party, in verifying, causes relay 286- to actuate and apply a guarding ground potential on the private bank contacts of the first branch of the conference trunk accesible to the various connectors, that this guardin tial endures until the said rfiay is caused to deactuate as set forth, and, therefore, no party can ainconnection with either branch of the con erence trunk under the condition. However, the release of each connector is individually controlled by its governing telephone, it can therefore be released from the conference connection by the part controlling it restoring his receiver upon t e switchhook, but due to the relay 286, being indeground poten endently held actuated dependent upon reay 230, the private bank contact in access to a released connector does not now become ungrounded until the supervising party restores is receiver on the switch hook at 'telephone m therewith.

operative method referred to at the outset is to be used, temporarily, perha s. Switchar'm.306 will be opened and swltch-arm 330 c Thus, a .party to the conference once withdrawing cannot agam obtam connection It will be assumed now, that the alternative has elapsed after wiper 296 stops on an en gaged bank contact, 298 for example, a circuit can be traced from grounded armature 300, wiper 296,-bank" contact 298, conductor 301 to the winding of relay 331 and the free terminal of lamp 332, causing the said relay to actuate'an'd the said lamp to glow.

After the supervising party believes the parties ordered in conference have come in on the first branch of-the conference trunk and he has called digit 1, causing switch element F to function one o cle and then rest at normal, causing switch e ement G to advance as described until its wi ers 296 and 297 rest on bank contacts 298 an 299 respectively due to three parties having connected with the first branch of the conference trunk and wiper 239 having encountered three grounded bank contacts, the following circuit condition will ensue u on a the retraction of rela 237 Ground rom armature 267 ,olf-norma spring 337, conductor 302, contact 303, to windin of relay 304, causing it to actuate. ground from armature 300 will cause relay 331 and lamp 332 to energize as set forth. A tone will be applied from source T2, conductor 305, interrupter 340, contact 341, conductor 342, switch arm 330, spring 307, conductor 308, armature 309, conductor 68 and over the before described tone path audible to the supervising party.

It will be mamfest that had wiper 239 encountered four bank contacts in lieu of three, and therefore wiper 296 rested on bank contact 314, the described circuit path from grounded armature 300 would be continued to energize relav 343 and 1am 344 in lieu of relay 331 and lamp 332, an the described tone path from tone source T2 and conductor 305 to conductor 342 would be h way of interrupter 345 in lieu of 340. T e latter interrupter and lamp is each indicative of four bus test bank contacts having been encountere by wiper 239, and that there are fourtelephones connected .with the first branch of and 54 to energize, deriving tone current trace circuit energizingrelay 304and also the through interrupters 350, 357 and 358 respectively.

The established tone path described 1ncluding the switch-arm 330 will endure and relay 304 will remain actuated until the supervising party calls digit 1 (or other diglt not indexing the number of busy test contacts engaged by wiper 239) and causes off-normal sprin ofset 0N3 to operate and open the tone path at spring 30 causing the tone to be disconnected from the second branch of the conference trunk and the first and second branches of the conference trunk to be established in conference relation.

It is manifest that if switch 306 is left 1n its operative position no' confusion will arise as switch F must be in off-normal position to make tone through said switch-arm 306 effective. Therefore, if in lieu of the ,said calling of digit 1 to cause the ap lied tone to cease, digit 3 (assuming that t ree grounded test contacts were engaged by wiper 239 and therefore wi er'296 rests on the bank contact 298) were ca 237 a circuit from winding of relay 304, contact 303, conductor 302, wiper 243, bank contact 277, conductor 301, ank contact 208, wiper 296 to grounded armature 300 would be established, causing relay 304 to actuate.

Then, tone from source T2, conductor 305,

switch-arm 306, spring 307, conductor 308,

armature 309 to conductor 68 and over the before described path audible to the supervising party will ensue. This tone being uninter rupted will now serve as a check upon the interrupted 'tone obtained b the first calling digit 1 and thereby hol ing open the last traced energizing path of relay 304.

. A counting device of meter RM is energized eve time motor magnet M is energized, the

- win ings of said meter RM and motor magnet M being in multiple relation. The counter RM, may be one of the well known forms of clcctro-magnetic counters, with the addition of the restoring button 361. The latter said button when depressed disengagcs the pawl 362 and causes the indicating member to retract to normal through the agenc of a retracting'spring 363. In other wor button 361 is provided for resetting the counter to zero .at will.

In view of the foregoing, it will be manifest that present invention has wide adaptations in the art, of course, modified in details of design depending upon its application. For example, one use would be to have wiper 239 accessible to private bank contacts of trunks. Then, by 0 erating relay 230 (perhaps independent 0 a telephone circuit) directly from a calling device the operator can ascertain audibly or by reference to the lamps or the countin led upon the retraction of relay device RM the number of busy trunks in t 6B e tested group, in fact in the present exampled instance the bankcontacta enga 'eable by wiper 239 may be assumed-to, b private contacts of a plurality of art only or as an am'pli cation ered in view of and within the e t e trunks. Of course, employing the resent invention in will be consi scope of the subjoined claims.

In the descriptions and in the drawings the connectors have all been assumed as accessible to local telephones in the private automatic exchange. It will be manifest that this I may also apply to connectors, such as trunk connectors that are not accessible to the local telephones directly, but are also accessible from telephones gaining connectionwith the private automatic exchan e through the-main office over a trunk line. fin such an event, the multiples shown as ap caring accessible to the local connectors W1ll b8 multipled, accessible to the trunk connectors as well. Thus, secret conferences may be held, not only between parties connected directly with the private automatic exchange, but may include a party or parties directliyl connected over a trunk with the main exc ange as well.

I The connectors A, B, O, D, and E are of a type which will not seize a set of bank contacts the private bank contact of which constitutes ground potential, and further, that will not seize unless the private bank contact constitutes battery potential, however, applying ground potential to the private bank contact (and its multiples) incident to the seizure. Connectors of well known types (and to seize upon not;

dependent upon receiving battery potential in order to seize, may be employed, introduci such obvious changes in the circuits (as the removal of the resistances disposed similarly to 201) as will adapt them. Having thus described an exam led form of one organization of the present invention, what I claim as new and desire to secure by U. S. Letters Patent is: i

1. In a telephone system, telephone lines, means for efiecting a common talking connection between a plurality of said lines, and means solely controlled over one of said lines for determining the number of lines connected together. a

2. In a telephone system, telephone lines, automatic switches controlled over said lines respectively for effecting a common talking connection between a plurality of said lines and means for determining from one of said lines the number of lines connected together. 3. In a telephone system, telephone lines means specific to each said line and controlled therefrom for eflectin a talking connection between a plurality 0 said lines and a common line upon request of a supervisor, and

means whereb the supervisor can determine from one of t e connected lines the number of lines connected together. I

4. In a telephone system, telephone lines,

means for efiecting a common talking connection between a p urality of said lines upon request of a supervisor, and means including automatic switch mechanism operated by the supervisor after the said connection has been efieeted for testing to determine whether the number of lines requested are so commonly connected together.

6. In a telephone system, telephone lines,

means for effecting a common talking connection between a pluralityof said lines upon request of a supervisor, a testing switch for counting the connected lines, means including the testing switch whereby the supervisor can determine from one of the connected lines the number of lines connected together, and for preventing additional lines from connectin with the common connection.

In a telephone system, a plurality of telephones and cooperating switc es a trunk normally accessible to the said telephones through he said switches simultaneously, and control means whereby one of the telephones havinlg attained connection withthe trunk may t ereafter at will prevent any other telephone thereafter attaining connection with the trunk.

8. In a telephone system, a plurality of telephones and cooperating automatic switches, a trunk normally accessible to the said telephones through the said switches simultaneously, and a tone source under positive directive control of one of the telephones connected with the trunk for applying the tone source audible to the latter telephone for verifying the number of telephones so connected.

9. In a telephone system a plurality of telephones a trunk normally simultaneously accessible to a plurality of the said telephones through "the said switches, a tone source, a first stepby-step switch and a second step-by-step switch, control means for causing the first 'ste -by-ste switch to automatically operate an cause t c said second step-by-step switch to'advance as many steps as there are telephones connected with the trunk, less one,

and means for then causing the first step-bystep switch to operate responsiveto the control means whereby the tone source may be applied through acircuit path set up by the operation of the step-by-step switches audiand cooperating automatic switches,

ble through one of the telephones connected "with the trunk.

10. Inatelephonesystem,apluralityoftelephones and coo crating automatic switches,

a common tru normally accessible to any number'of the said telephones simultaneously through the said switches respectively, a branch of the said trunk accessible to one of the said telephones through any one of the said switches, a tone source, a first and a second setting switch, control means at the telephone connected to the said branch for causing the said'first switch to automaticall operate and thus cause the second said switch to advance as many steps as there are telephones connected to the common trunk, and means for then causing the said first setting switch to operate in response to the control means whereby the tone source may be applied over a circuit path set up b the operation of the setting switches an ible to the telephone on the branch.

11. In a telephone system a plurality of telephones and cooperating switches, a trunk consisting of a first and a second branch normally accessible to the said telephones simlutaneously, a tone source, a first and a second setting switch, means for a plurality of the telephones gaining connection with the said first branch and for one of the telephones only gaining connection with the said second branch, control means operable from the telephone gaining connection with the said second branch whereby the said first switch will be caused to operate and set up a condition in the said second switch indicz'itiveof the number of telephones connected with thesaid first branch, means controllable through the second branch for causing the said first switch to operate andset up a condition in the said second switch indexin the number of telephones connected to t e said first branch and means for applying the tone audible to the party on the said second branch if the number of telephones on the said first branch corresponds to'the condition set up in the said second switch by the said first switch.

12. In a telephone system a plurality of telephones and cooperating switches, a trunk consisting of'a first and a second branch normally accessible to the telephones, atone source, a setting device,means in control of a telephone on one of the said branches for setting up a condition in the setting device indexmg the number of telephones on the other said branch, and means including the setting device whereby the tone will be applied audible through the controlling telephone, verifying the number of telephones connected to the other said branch.

13. In a telephone system a first switch for testing the busy or idle stateof a plurality of test contacts, a second switch cooperating with attend first switch which will function in correspondence with the busy conditions found by the said firstswitch but not the idle conditions found thereby, and means includ- 'not the idle conditions. found thereby, and

means including the second switch control- 7 lable from the testing telephone for ascertaining the number of test contacts by the said first switch. l

15. In a telephone system a conference trunk having two branches in normal talking-relation, a plurality of telephones having found busy access to both branches of the said trunk,

means so each of a plurality of the said telephones can independently ain connection with a first branch of the sai trunk simultaneously, means so but one of the said telephones can independently gainconnection with asecond branch of-the said trunk, and meansv controlled by the telephone gaining connection with the said second branch for thereafter at will guarding the said first branch against subsequent seizure.

16. In a telephone s stem a conference trunk, a plurality of te ephones having access to the trunk simultaneously, and means controlled b a telephone connected with the trunk for t ereafter at will guarding the trunk against subsequent seizure.

17. In a telephone system a conference trunk, a plurality of telephones having simultaneous access to the trunk through switches cooperating with sets of bank contact sets, and means controlled by one of the telephones connected with one of the sets of bank contacts for thereafter at will guarding any of the unseized sets of bank contacts against seizure.

18. In a telephone system a testing telephone, a switch for testing-the busy or idle state of a pluralit of trunk test contacts, a means controlled y the first switch for recording by its set-up condition'the number of test contacts found busy by the switch but not the idle conditions found thereby, means including the second switch for initiating the functioning of the switch, and means for gvidencing the number of test contacts found 1?) In a telephone system a plurality of telephones and coo erating automatic Switches, a common trunh normally simultaneously accessible to the said telephones throu h the said switches, a tone source, a plurafity of sets of trunk test terminals, a

1,714,aos

testing switch, a recording device, means for initiating the functioning of the testing switch and for causin set-up a condition in native of the number of sets of busy trunk'terminals. tested by the testing switch and means-including the tone source'for indicating the number of sets of busy test terminalstested. 20. In a telephone system a plurality of, telephones and coo rating automatic switches, a common trun normally simultaneously accessible to the. said telephones through the said switches, indicating lamps, a plurality of sets of trunk test terminals, a testing switch, a reoordingdevice, means for initiating the functioning of the testing switch and for causing the recording device to set up a condition indicative of the number of sets of busy trunk terminals tested by the testing switch, and means includin the indieating lamps for indexing the num r of sets of bus test terminals tested.

21. n a telephone system a conference trunk simultaneously accessible to a plurality of telephones through connecting means, a tone source, a test switch, means under control of a first telephone connected with the trunk for initiating the functioning of the test switch, and. means automatically controlled by the'test switch for applying the tone source audible'to the said first telephone to index the number of telephones connected on the conference trunk.

22. In a telephone system a conference trunk simultaneously accessible to a plurality of telephones through connecting means, a tone source,a test switch, means under control of a first telephone connected with the trunkfor initiating the functioning of the test switch, and means automatically controlled by the test switch for applyin the the recording device to tone source audible to the said first telep one to index the number of telephones connected on the conference trunk' and for guarding the trunk against further connection.

23. In an automatic switching system, a calling line, a switch, a calling device means for connecting the calling line with the switch, means controlled by the calling device for initiating the primary movement of the switch from normal position while maintain-J ing the connection whereby the switch will then self automatically restore to normal position, and means eflective consequent upon the :said operationfor disabling .the said self automatic operation and rendering the switch subject to ste -by-step directive control from I ing switch step-by-st 25. In mechanism f dr testing the busy or idle state of'each trunk of a group of trunks, test contacts individual to each trunk aecessiblo to a test wiper of the mechanism, means for initiating the functioning of the mechanism, and means for setting up a condition in the mechanism controlled by the test contacts found busy but not controlled by the test contacts found idle which will index the number of busy trunks in the group.

26. In, a telephone system a plurality of telephones and cooperating switches, a trunk consisting of a first and a second branch normally accessible to the telephones, a tone source, a setting device, means in control of a telephone on one of the said branches for setting up a condition in the setting device indexing the number of telephones on the other said branch, and means including the setting device whereby the tone will be applied audible through the controlling telephone only, verifying the number of telephones connected to the other said branch.

27. In a telephone systema plurality of telephones and cooperating switches, a trunk consisting of a first and a second branch nor-- mally accessible to the telephones, a tone source, a setting device, means in control of a telephone on one of the said branches for setting up'a condition in the setting device indexing the number of telephones on the other said branch, and means including the setting device whereby the tone will be applied audible through the controlling telephone only, verifying the number of telephones connected to the other said branch, if the said set-up condition indexes the number of telephones actually connected to the other said branch.

' 28. In a telephone system a plurality of telephones and cooperating switches, a trunk consisting of a first and a second branch normally accessible to the telephones, a tone source, a setting device, means in control of a telephone on one of the said branches for setting up a-condition in the setting device indexing an arbitrary number of telephones which may be connected to the other said branch, means including the setting device whereby the tone will be a plied audible through the controlling telep 10118 to verify the number of telephones connected to the other said branch if the said setup condition indexes the number of telephones actually connected to the other said branch, and means for disassociatin the tone source.

29. In a telephone system a lurality of telephones and cooperating switc es, a trunk consisting of a first and a second branch normally accessible to the telephones, a tone source, a setting device, means in control of. a telephone on one of the said branches for setting up a-condition in the setting device inde'xing an arbitrary number of telephones which may be connected to the other said branch, and means including the setting device whereby thetone will be applied audible through the controlling telephone to verify the number of telephones connected to the other said branch if the set up condition indexes the number of telephones actually connected to the other said branch.

80. In a telephone system a testing telephone, a line leading from the testing telephone to a first automatic switch, the switch for testing the normal and abnormal state of a plurality of test contacts, a second switch operated by the said first switch in corres 0ndence with the number of test contacts ound abnormal by the said first switch, and means including the first switch controlled from the testing telephone operable at will for ascertainin g the number of test contacts found abnormal by the said first switch.

31. In a testing system a testing station, a line leading from the testin station to a first automatic switch, the switc for testing the normal and abnormal state of a plurality of test contacts, a second. switch operated by the said first switch in correspondence with the number of test contacts found abnormal by the said first switch, and means operable at will over the said line after the testing operations have been completed for indexing the number of test contacts found abnormal by the said first switch.

32. In a testing system a testing station, a I

mechanism primarily controlled from the said station for thereafter automatically testmg test contacts wherein each said test contact manifests one of two conditions respectively, test contacts manifesting the two conditions, each said test contact manifesting one said condition, means for automatically setting up a condition in the mechanism depending upon the number of test contacts tested which manifest a predetermined one of said two conditions, and means including the said mechanism for evidencin only the number of test contacts tested whic manifest the said predetermined condition.

33. In a telephone system a testing station, a mechanism primarily controlled from the said station for thereafter automatically testing line busy-test contacts of telephone lines wherein each said test contact manifests a busy or an idle condition respectively, test contacts manifesting the two conditions,

- tion in the mechanism depending upon the number of test contacts tested which manifest abusy condition, and means includmg. the

said mechanism for evidencing only the num- 'ber of test contacts tested which manifest the 'busy condition.

34. Ian telephone system a testing station, a mechanism primaril controlled from the said station for therea ter automatically testing line busy-test contacts of telephone lines wherein each said test contact manifests a busy or an idle condition respectively, test contacts manifesting the two conditions, and means for automatically setting up a condition in the mechanism depending upon the number of test contacts tested which manifest a busy condition.

35. In a telephone system a testing station, a mechanism primaril controlled from the said station for therea ter automatically testing line busy-test contacts of telephone lines wherein each said test contact manifests a busy or an idle condition respectively, test contacts manifesting the two conditions, and means for automatically setting up 'a condition in the mechanism depending upon the number of test contacts tested which manifest a busy condition to indicate at the testing station the number of lines found busy.

36. In a telephone system a testing station, a line, a mechanism primarily controlled over the line from the said station for thereafter testing line busy-test contacts of a group of telephone lines automatically wherein each said test contact manifests a busy or an idle condition respectively, a tone source, test contacts manifesting the two conditions, and means for automatically setting up a condition in the mechanism depending upon the number of test contacts which manifest a busy condition when tested to apply the tone source over the line to the testing station to indicate the number of busy lines tested.

37. In a telephone system a test-in station,

.a mechanism primarilfz controlled rom the said station for therea r automatically testing test contacts wherein each said test contact manifests one of two conditions respectively, test contacts manifesting the two conditions, each said test contact manifesting'one said condition, and means for automatically setting up a condition in the mechanism depending upon the number of test contacts tested which manifest a predetermined one of said two conditions. i

38. In a testing system a testing station, a mechanism primarily controlled from the said station for thereafter automatically testing test contacts wherein each said test contact manifests one of a pluraliy of conditions respectivel test contacts manifesting the plurality 0 conditions, each said test contact manifesting one said condition, and means for automatically setting up a condition in the mechanism depending upon the number of test contacts tested which manifest a predetermined one of said plurality of conditions. 4

39.. In a testing system a testing station, a mechanism rimarily controlled from the said station or thereafter automatically testing test contacts wherein each said test contact manifestsone of a. plurality of conditions respectively, test contacts manifesting the plurality of conditions, means for automatically setting up a condition in the mechanism depending upon the number of testcontacts tested which manifest a predetermined one of said lurality of conditions, and means including t e said mechanism for evidencing only the number of test contacts tested which manifest the said predetermined condition.

40. In a testing system a group of bus test contacts corres onding respectively to t e lines of a group 0 busy and idle lines, a test mechanism, means for causing the test mechanism to operate whereby to test the said contacts, and means for indicating the number of busy lines in the group;

41. In a telephone system a trunk line, a plurality of connection points at which connectlon can be made to the trunk line. from connecting lines, a plurality of said connecting lines, means on the respective said connecting lines for connecting the said connect ing lines to the trunk line through the connection points respectively, the number of said connecting lines possible of connection to the trunk line not exceeding thenumber of said connection points, and means controlled from one of said plurality of connecting lines connected to the trunk line to indicate how many connecting lines are then connected to the trunk line and to bar the trunk line from beingthereafter being connected to by a connecting line through an unconnected connection point.

42. In a telephone system a trunk line, a

connecting lines, a plurality of said connect-=- ing lines, means for connecting the said connecting lines to the trunk line through the connection points respectively, the number of said connecting lines possible of connection to the trunk line not exceeding the number of said connection points, a lesser number of connectinglines being connected to the trunk than there are connection points, and means controlled from one of sald plurality of connecting lines connected to the trunk line to indicate how many lines are connected to the trunk line through an unconnected connection point.

43. In a telephone system a trunk line, a plurality of connection points at which connection can be made to the trunk line from connecting lines, a plurality of said connecting lines, means for connecting the said connecting lines to the trunk line through the connection points under control of the respective connecting lines, the number of said connecting lines possible of connection to the trunk line not exceeding the number of said connection points, a lesser number of connecting lines being connected to the trunk than there are connecting oints, and means controlled from one of sand plurality of connect ing lines connected to the trunk line to indicate how many lines are connected to the trunk line. j

44. In a telephone system a trunk line, a plurality of connecting points at which conmotion can be made to the trunk line from connecting lines, a plurality of said connecting lines, means for connecting the -sa '-;i connecting lines to the trunk line througlrthe connection points under automatic switch control from the respective connecting lines, a lesser number of connecting lines being connected to the trunk line than there are connecting points, and means to indicate how many lines are connected to the trunk line.

45. In a telephone system a trunk line, a plurality of connecting points at which connection can be made to the trunk line from connecting lines, a plurality of'eonnecting lines, means for connecting one or more of the i said connecting lines to the trunk line through a corresponding number of connection oints under automatic switch control from t e respective connecting lines, a tone source corresponding to each plurality of connecting lines which may be connected to the trunk line, and means for automatically applying the tone source indicative of the number of connecting lines connected to the trunk line.

46. In a telephone system, a calling subseribers line, an automatic switch associated therewith, called lines accessible thereto, ,a calling device under the control of said calling subscriber for operating said switch into engagement with one of-said called lines without making the same busy, and means respon SlVe to the reoperation of said Cflllll'lgdBVlCG for preventing another connection being established with the connected line. a

47. In a telephone system, a calling subscribers line, an automatic switch associated therewith, called lines accessible thereto, a ealling device under the control of said calling subscriber for operating said switch into engagement with one of said called lines without making the same busy, anda relay ener-v gized in response to the reoperation of said calling device for applying a usy potential to said called line.

48. In an automatic telephone system, a

conference line, branches of said conference line, a plurality of calling telephone lines, au-

tomatic switches, means for automatically op crating certain of'the switches toconnect corresponding said telephone lines in talking relation with individual branches of said conference line, means whereby all said connected telephone linesthereby become in mutual talking relation, means operated over one of said telephone lines connected for preventing an additional said telephone line from becoming in talkingrelation with an unconnected branch of the conference line means whereby one of the connected lines can be disconnected from the conference line branch to which it was connected, and means for preventing a substituted connection over the latter said branch without specific directive operation therefor.

V 50. In a telephone system, a group of busytest contacts corresponding respectively to the lines of a group of busy and idle lines, a test mechanism, means for causing the test mechanism to operate whereby to test the said contacts, a plurality of tone sources, and means for applying any one of said tone sources to produce an audible sound wherein the specific said tonesource applied will be determined by the number of lines which are busy in the group at the time the a test mechanism is operated.

i In: witness whereof, I hereunto subscribe naine this 21st day of February, A. D. 9 1: f

v HERBERT M. FRIENDLY. 

